This invention relates generally to methods and apparatus for breaking frangible substrates, and more particularly to the breaking of brittle semiconductor wafers and the like to separate the wafer into individual dies.
In the manufacture of microelectronic devices, such as integrated circuits and the like, a plurality of such devices are fabricated as individual dies on a single semiconductor wafer. The wafer is then separated into individual dies utilizing semiconductor scribing and breaking equipment. Wafer scribing may be performed with saws, sharp diamond-pointed scribing tools or lasers to form stress lines on the wafer along which the wafer will be broken to separate the individual dies. Wafers are broken along the scribe lines by applying tensile strain across the scribe line sufficient to cause the wafer to break. This may be accomplished in different ways. In one known form of wafer breaking apparatus shown in U.S. Pat. No. 5,820,006 to Turner, assigned to the assignee of the present invention, a scribe line is aligned with a straight sharp blade of an impulse bar, and the sharp edge is forced to impact the bottom surface of the wafer directly beneath the scribe line, bending the wafer upwardly and placing the upper surface of the wafer under tension along the scribe line opposite the sharp edge. Another known form of breaking apparatus is disclosed in U.S. Pat. No. 5,458,269 to Loomis in which the wafer is supported on the plane surface of a mandrel having a sharp edge. A scribe line on the wafer on is aligned along the edge. A break wheel having either wheel profiles which engage the upper surface of the wafer on opposite sides of the scribe line or a compliant surface that rolls over the wafer along the scribe line causes the wafer to bend over the edge and break along the scribe line. The tensile strain applied to the wafer is adjusted by varying the angle of the break plane surface of the mandrel which supports the wafer relative to the break wheel.
Known breaking apparatus typically require close alignment between the scribe line along which the wafer is to be broken and the breaking mechanism of the apparatus. With the Turner apparatus of the '006 patent, this requires accurate alignment between the straight blade of the impulse bar and the scribe line, and with the Loomis apparatus, it requires close alignment of the scribe line relative to the break edge of the mandrel, and close alignment of the profile members of the break wheel to the scribe line. To accommodate a varying or different pitch between scribe lines, as, for example, for dies having a non-square profile or for wafers having different size dies, readjustment of the mechanism to accommodate the different pitches may require changing components of the breaking apparatus and involve substantial set-up time. Moreover, the contact force applied to the wafer by the breaking apparatus must be adjusted to avoid damage to sensitive components on the wafer as well as to avoid unwanted breaking of the wafer at places other than along the desired scribe line.
Another important factor that impacts breaking is that the size of parts to be broken has gotten smaller over the years. Due to the physics of breaking a part with a small ratio between die size and substrate material thickness, not only has the alignment become more critical, but also the force required to cause the break has grown. This imposes a greater requirement with known breaking apparatus for accurate alignment between the scribe lines to be broken and the breaking element, such as a breaker bar or edge, particularly the alignment with respect to the theta (rotary) axis. This contributes to an increase in the difficulty of breaking such parts.
It is desirable to provide breaking apparatus which avoids these and other problems of known devices by accommodating wafers with different die pitch, wafers of different materials and/or different thicknesses which may require different breaking forces, affords automated operation with quick and easy set-up, and is able to accommodate easily dies with different pitches. It is to these ends that the present invention is directed.